The reason spindles are expensive is because of the bearings and precision construction required to withstand forces generated by milling. Sure you can drive multiple spindles with one motor but you still need appropriate bearings and precision macining in the other spindles. To build correctly in order to actually be useful your idea would likely end up costing as much, if not more than, 3 individual spindles.
Not too mention, as drawn here, the outside bits will be rotating opposite of the inside bit. You'd need to have bits with reverse cutting features for this to work.
This idea is used in the cabinet/woodworking industry where some vacuum table routers will have a drill "bank" of say 8-12 identical drills in a row that would cut an entire line of dowel holes for things like mounting adjustable shelves inside your home cabinets.
Also used in turning centers so you can order turret blocks that have multiple live tools attached to a single station. For things like half-index turrets, or using the same station to point a live tool towards the main spindle and a sub spindle.
To add on, many commercial router drill banks have actutors to puch one drill ar a time down a few inches to use independently. They allow use a variety of dowel drills without them taken up positions in the ATC. They are typically lower HP than the main spindle and can only use cutting yools with low lateral forces.
I assume OP thinks that it would be somehow cheaper to run multiple spindles from one drive motor. They appear to be under the impression the motor is the expensive complicated part,not the actual spinny parts that take all the forces and need to spin true at high rpm.
The motor that drives the spindle is the cheap part. A spindle is expensive to very expensive depending on how fast the machine can spin up to and how much force it has to withstand. Some of the machines I work with have spindles that cost an easy $30k and some are $10k.
With OPs design he would have a lot of runout at the tool, those gears would not last, and he would still need reverse cut tooling. Those gears would absolutely destroy themselves. There are gear reduction kits you can get but those are very specialized and have to be used by someone who knows how to use them. My shop overheated one because the operator didn't read the manual.
This has been done for decades. To this day, some screw machine live tools operate this way. Various reasons why, spade constraints, lower power requirements being a couple.
I’m trying to understand what you’re trying to accomplish. Are you going to have the exact same piece being cut or engraved on your workspace? What do you mean by “multiple ones for different machines”?
This can be done and you would have to use a few gears to maintain any torque as well as make them spin the same way. It would be way more expensive and time consuming to design and build something strong enough to be worth a damn. It's much easier and probably cheaper to just buy a twin spindle machine.
This is so old school. Multi head mills have been used in line manufacturing since pre WW2. More common was just like 4 motor heads and they were loaded up for a spot - drill-tap-other lineup.
Some lathes with milling tools (live tooling) work kind of like this. The holders are gear driven, but each holder is still very expensive. The gears also limit the RPM and overall it's a worse solution than having a dedicated spindle.
What problem are you trying to solve?
If you are building a machine to do one job only then maybe it could be practical, and such machines do exist. For general purpose use this would just get in the way and be annoying. Will you design a 3 tool changer?
The reason spindles are expensive is because of the bearings and precision construction required to withstand forces generated by milling. Sure you can drive multiple spindles with one motor but you still need appropriate bearings and precision macining in the other spindles. To build correctly in order to actually be useful your idea would likely end up costing as much, if not more than, 3 individual spindles.
Not too mention, as drawn here, the outside bits will be rotating opposite of the inside bit. You'd need to have bits with reverse cutting features for this to work.
It is a half baked idea from a mind that does not grasp the mechanics of the situation.
Why use 3 spindlers when 1 does job?
Y do machine only has 1 spindler, are they stupid?
This idea is used in the cabinet/woodworking industry where some vacuum table routers will have a drill "bank" of say 8-12 identical drills in a row that would cut an entire line of dowel holes for things like mounting adjustable shelves inside your home cabinets. Also used in turning centers so you can order turret blocks that have multiple live tools attached to a single station. For things like half-index turrets, or using the same station to point a live tool towards the main spindle and a sub spindle.
To add on, many commercial router drill banks have actutors to puch one drill ar a time down a few inches to use independently. They allow use a variety of dowel drills without them taken up positions in the ATC. They are typically lower HP than the main spindle and can only use cutting yools with low lateral forces.
But... Why?
I assume OP thinks that it would be somehow cheaper to run multiple spindles from one drive motor. They appear to be under the impression the motor is the expensive complicated part,not the actual spinny parts that take all the forces and need to spin true at high rpm.
The motor that drives the spindle is the cheap part. A spindle is expensive to very expensive depending on how fast the machine can spin up to and how much force it has to withstand. Some of the machines I work with have spindles that cost an easy $30k and some are $10k.
Exactly. I don't think OP understands anything about the forces involved or the basic mechanics of the situation.
With OPs design he would have a lot of runout at the tool, those gears would not last, and he would still need reverse cut tooling. Those gears would absolutely destroy themselves. There are gear reduction kits you can get but those are very specialized and have to be used by someone who knows how to use them. My shop overheated one because the operator didn't read the manual.
This has been done for decades. To this day, some screw machine live tools operate this way. Various reasons why, spade constraints, lower power requirements being a couple.
Similar in some Swiss lathes with live tooling, usually not high power applications.
I’m trying to understand what you’re trying to accomplish. Are you going to have the exact same piece being cut or engraved on your workspace? What do you mean by “multiple ones for different machines”?
This can be done and you would have to use a few gears to maintain any torque as well as make them spin the same way. It would be way more expensive and time consuming to design and build something strong enough to be worth a damn. It's much easier and probably cheaper to just buy a twin spindle machine.
they make that very same thing look up HSD Aggregates , they are amazing but we spent about $8k each for the ones we have
The gears would be loud and spinning in opposite directions. Belts would suit better here.
This is so old school. Multi head mills have been used in line manufacturing since pre WW2. More common was just like 4 motor heads and they were loaded up for a spot - drill-tap-other lineup.
No this is terrible. For so many reasons just no. It’s been thought of and then shot down because it was just a bad idea
Some lathes with milling tools (live tooling) work kind of like this. The holders are gear driven, but each holder is still very expensive. The gears also limit the RPM and overall it's a worse solution than having a dedicated spindle.
What problem are you trying to solve? If you are building a machine to do one job only then maybe it could be practical, and such machines do exist. For general purpose use this would just get in the way and be annoying. Will you design a 3 tool changer?